a. Field of the Invention
This invention relates to apparatus for joining yarns or filaments.
B. Description of the Prior Art
When operating textile machinery involving the handling of running yarns, it is often necessary to join two ends of yarns together. For example, when changing supply packages of yarn it is desirable, in order to avoid restringing the machine, to join the end of one package to the beginning of the next. Several ways of doing this have been proposed but it is most usual to knot the two ends of the yarn together, a method which has normally been successful where the yarns were in a drawn state. With undrawn yarns, however, difficulties arise when an attempt is made to apply sufficient tension to the knot in order to make it secure, because the application of such tension merely causes the yarn to be drawn. The resulting presence of a few centimeters of drawn yarn, in a yarn that is on the whole undrawn, causes problems when the yarn is later processed. If the further processing includes a drawing step, the few centimeters of drawn yarn close to the knot may become overdrawn or may even break. Even if the yarn does not break, the overdrawn portion of the yarn presents a different appearance when dyed from the appearance of yarn which has been drawn only to the proper extent. It also has a lower tensile strength and when textured has inferior crimped characteristics.
It has been proposed to draw the ends of two undrawn yarns and join them by a knot so that there is substantially no undrawn yarn forming the knot and there is substantially no drawn yarn outside the knot. The present invention is concerned with an apparatus for knotting together two undrawn yarns so as to form a joint of this kind.